I can understand why they do that. Many folks don't like to deal with the extras. Although, with us, we just sell them. I ordered from Ideal and they
sent 3 extras(chickens not ducks) with my small order. I picked the ones I wanted to keep and sold the rest. However, a lot of folks don't like to do that.
Also, with a small order, they might put in a heating pad or a better insulated box. That helps them stay warmer with less chicks. It also makes it more expensive for them to ship.